1. Field of the Invention
The invention relates to a micro-fluid injection device, and in particular to a piezoelectric fluid injection device and a driving voltage calibration method thereof.
2. Description of the Related Art
Recently, fluid injection has been widely utilized in various devices such as inkjet printers and the like. As micro-system engineering increasingly develops, such devices can be further applied in other fields, for example, fuel injection, cell sorting, drug delivery, print lithography, and micro-jet propulsion systems. Inkjet applications generally utilize continuous or drop-on-demand supply.
Conventional fluid injection devices also comprise thermal bubble and piezoelectric diaphragm drive types.
A conventional control circuit of a piezoelectric inkjet printhead is shown in FIG. 1. A piezoelectric inkjet printhead 10 includes a plurality of nozzles 1˜X such as 1˜128. Each nozzle's equivalent circuit represents parallel equivalent capacitors CL1˜CLX. Each nozzle is driven by a driving cell 20. Conventionally, the nozzles of printhead are driven by a fixed driving voltage, such as 100V. However, impedance variations among nozzles are produced due to operational variations in piezoelectric diaphragm process or ageing, resulting in formation of various droplet volumes, or even, for some nozzles, no droplets being ejected therefore when the fixed driving voltage is applied, seriously affecting utilization efficiency of the inkjet printhead.
Additionally, variations in fluid pressure resulting from alternation of fluid resistance or material property around nozzles may also cause such drawbacks.
U.S. Pat. No. 6,286,922 discloses a method of controlling a driving voltage of a piezoelectric inkjet printhead and a feedback procedure. An output driving voltage from a control system is switched via an analog/digital converter and fed back. The feedback voltage is then determined by comparison with an actual required driving voltage by the control system and modified.
U.S. Pat. No. 6,286,922 discloses a driving circuit and a control system of a piezoelectric inkjet printhead, capable of controlling ejected droplet volumes and providing preferred printing quality.